January 3 – The Ratho rail crash in which NBR H class locomotive 874 Dunedin in charge of the Edinburgh to Glasgow express train was in collision with a light engine at Queensferry Junction, leaving 12 people dead and 46 seriously injured. The cause was found to be inadequate signalling procedures.[1]

February 24 – WWI: United States ambassador to the United Kingdom, Walter Hines Page, is shown the intercepted Zimmermann Telegram, in which Germany offers to give the American Southwest back to Mexico if Mexico declares war on the United States.

President Woodrow Wilson of the United States announces to Congress the breaking of diplomatic relations with Germany

The Parliament of Finland, with a Social Democratic majority, passes a "Sovereignty Act", declaring itself, as the representative of the Finnish people, sovereign over the Grand Principality of Finland. The Russian Provisional Government does not recognize the act, as it would have devolved Russian sovereignty over Finland, formerly exercised by the Russian Emperor as Grand Prince of Finland and alter the relationship between Finland and Russia into a real union with Russia solely responsible for the defence and foreign relations of an independent Finland.

October 12 – WWI: First Battle of Passchendaele: Allies fail to take a German defensive position with the biggest loss of life in a single day for New Zealand, over 800 of whose men and 45 officers are killed, roughly 1 in 1000 of the nation's population at this time.

Carl Swartz leaves office as Prime Minister of Sweden after dismal election results for the right-wing in the Riksdag elections in September. He is replaced by liberal leader and history professor Nils Edén.

October 23 – A Brazilian ship is destroyed by a German U-Boat, encouraging Brazil to enter World War I.